Air-raid-warning signal generator



June 13, 1961 M. JEANMONOD ETAL 2,988,599

AIR-RAID-WARNING SIGNAL GENERATOR nvmvrozes HUGHES M BLOWERS M/CHELJEANMONOD 5 BY A, M,

ATTORNEY 52; mm mw ou M25 NF mw VD Filed June 28, 1960 United StatesPatent AlR-RAID-WARNlNG SIGNAL GENERATOR Michel Jeanmonod, Mill- Valley,and Hughes; M. Blowers,

Berkeley, Calif.,, assignors, by mesne assignments, to

Sound Communication Products, Inc., doing business as Sound Products ofCalifornia, San Francisco, Calif.,

a corporation of California Filed June 28, 1960, Ser. No. 39,395 7Claims. (Cl. 179-2) The present invention relates to electronic signalgenerartors in general and is particularly directed to an interval-timedsignal generator for furnishing air-raid warning signals for eithermanually operated or automatic distribution to sound systems.

It has: become standard practice for air-raid-warning purposes to sounda steady alert tone for a duration of, for example, four minutes toalert the populace to enemy aircraft approaching at relatively longrange. When the aircraft are in striking range, a wailing take covertone or siren is sounded for a duration of, for example, three minutesto indicate the impending disaster and warn the populace to take allpossible protective measures against air attack. In order that thewarning procedurev be carried into elfect, means must be provided at allpopulation centers, suchas, schools, manufacturing plants, airports,stores, sports arenas, and the like, as well as upon city streets, toproduce the airraid-warning sound signals at a moments notice. Moreover,it. is. desirable that the warning signal generating means be adaptedfor use with existing public-address or other sound systems as well asin city-wide warning systems controlled from a remote central commandlocation.

It is, therefore, an object of the present invention to provide anair-raid-warning signal generator for furnishing air raid warningsignals which may be distributed throughout central sound or localpublic address systems.

Another object of the invention is the provision of anair-raid-warningsignal generator that may be manually or automatically controlled torelease the warning signals.

It is: yet another object of the invention to provide a signal generatorof the class described which has provision to insure the warning signalscomplete priority of the input circuit of an existing sound system intowhich the generator is connected.

It is still another object of the invention to provide anair-raid-warning signal generator for the selective generation of asteady tone alert signal and a wailing tonelorsi-ren take-cover signalboth having adjustable automatically timed durations.

It is a further object of this invention to provide a signal generatorof the class described wherein the takecover signal has priority overthe alert signal.

It is an even further object to provide an interval timed electronicsignal generator which is maintained in a low power consumptionstand-bycondition until actuated to generate the signals.

A still further object of the invention is the provision of anair-raid-warning signal generator which is capable of automaticallyswitching external priority relay circuits.

Further objects are to provide a construction of maximum simplicity,economy and ease of assembly and dis-- assembly, also such: furtherobjects, advantages and capabilities as will fully appear and as areinherently possessed' by the device and invention described herein.

Theinvention further resides in the combination, con struction andarrangement of parts illustrated in the accompanying drawing, and whilethere is shown. therein a preferred embodiment thereof, it is to beunderstood that the same is illustrative. of they invention and. that,

the: invention is capable of modification and change and comprehendsother details of construction without departing from the spirit thereofor the scope of the appended claims.

Referring to the drawing, the single FIGURE of the drawing is adiagrammatic circuit for carrying out the present invention.

The single FIGURE is a schematic wiring diagram of a preferredembodiment of a signal generator in accordance with the invention asemployed with an existing sound system.

Referring now to the single FIGURE of the drawing, there is shown anair-raid-warning signal generator 10 which is arranged to furnish timedsteady tone alert signals and wailing tone take-cover signals to anaudio outlet 11 in respective response to actuation of alert andtake'cover push buttons 12, 13, or to remote push buttons or relayscoupled to the unit by connection of control lines to a control outlet14. The unit is also arranged to provide automatic switching forexternal priority relay circuits which may be connected to the controloutlet 14. The warning signals may be distributed to acentral' soundsystem coupled to the audio outlet 11, or to, for example, an audioamplifier 16 comprising the input of an existing public-address systemcoupled to the outlet as shown in the FIGURE. In the latter instance,the normal use of the amplifier 16 with various program sources such asa microphone 17 is retained. However, the generator 10 includesprovision to insure the warning signals priority over the programsources upon generation of-such signals.

Considering now the signal generator 10 as to its detailed circuitarrangement for theaccomplishment of the foregoing ends, the geenratorincludes a toneoscillator circuit 18 comprising a. variable frequencytone oscillator section 19 for producing the steady ale signal and slowtuning tone oscillator section 21 for producing the wailing take-coversignal. The tone sections 19, 21 are preferably provided as conventionalmultivibrator connected duo-triodes 22 and 23, respectively, the latterhaving a bias capacitor 24 for establishing a slowly varying grid biasvoltage. at the duotriode 23- productive of the slow tone variation inthe output thereof. The plate. outputs of both tubes are coupled to avolume control 26 which facilitates adjustment of the signals to thedesired. sound level.

Operating power for the tone oscillator circuit '18 is provided fromapower supply 27 of generally conventional design. More specifically,the supply includes a power transformer 28 having a primary 29'connected to a plug 31 for insertion into a commercial power receptacle.The secondary 32 isv appropriately tapped toprovide a low. voltagefilament output between taps 33-, 34,. such taps being connected to thefilaments of. the tone oscillator duo-triodes 22, 2-3. In. addition,taps 36, 37 and 38, 39 areprovided in the secondary 32 to furnish,respectively, plate and filament voltage to a duo-diode 41, connected asa full wave. rectifier. The direct cur-- rent output. of the rectifiertube 41 is in turn coupled to the plates of the. tone oscillatorduo-triodes 2:2, 23 to provide plate bias. therefor. One further outputis included from the power supply 2.7 for purposes subsequentlydescribed, such output being low voltage directed. cur-- rent asproduced, for example, by means of opposed dry disc type rectifiers 42,43 connected between the filament taps 33, 34 of the power transformersecondary.

In, order that the tone oscillator circuit 18 be maintained in a lowpower consumption stand-by condition with only the filaments of thetubes 22', 23 energized until such time as it is desired to generate thetone warning signals, means are provided for the selective switching.of. the plate. bias output of power supply 27 on and 0E.

More particularly, a power supply switching relay 44 having an operatingcoil 46 and contactors 47, 48, respectively, operating between normallyclosed contacts 49, 51 and normally open contacts 52, 53 is provided forthis purpose. The contactor 47 is connected to the ground bus of thepower supply and tone oscillator circuits whereas normally open contact52 is connected to a center tap 54 between the plate voltage taps 36, 37of power transformer 28. Thus, until the relay coil 46 is energized, thecenter tap 54 is floating, and unsymmetrical voltages are applied fromtaps 36, 37 to the plates of rectifier tube 41, such voltages beingincompatible with the generation of a high voltage direct current outputtherefrom. Upon energization of the relay coil, contactor 47 engages thenormally open contact 52 to thereby connect the center tap 54 to ground.Symmetrical oppositely phased voltages with reference to ground are thusgenerated at taps 36, 37 which are conducive to the full wave operationof the rectifier tube 41 and generation of the plate bias therefromrequired for the operation of the tone oscillatorcircuit 18. Thecontactor 48 and normally closed and normally open contacts 51, 53 playno part in the operation of the power supply 27 and tone oscillatorcircuit 18 but rather are employed herein to accomplish the previouslymentioned automatic switching of external priority relay circuits or thelike. To this end, the contactor 48 and contacts 51, 53 are respectivelyconnected to separate pins of the control outlet 14 such that uponconnection of external circuits thereto, automatic switching thereof isaccomplished by the relay 44.

As noted previously, it is desirable that the alert and take-cover tonesignals generated by the tone oscillator circuit 18 be separately timedfor intervals of, for example, four minutes and three minutes,respectively. In accordance with the present invention, this isaccomplished by timed-interval energization of the coil 46 of powersupply control relay 44. More particularly, alert and take-cover timers56. 57 are provided to actuate relay 44 for predeterminedtime-intervals; e.g., four minutes and three minutes, respectively, inresponse to closure of the alert and take-cover switches 12, 13 orequivalent triggering of the signal generator into operation. The timersare similar in design and are preferably substantiallv conventionalimpulse o erated. synchronous motor driven timers with variable time setreleases. The timers 56. 57 may, for example, respectively includesynchronous motors 58, 59 having their stators 61. 62 parallel connectedto the power plug 31. The rotors 63. 64 f these motors are shaftconnected through clutches 66. 67 to cams 68. 69 having pawls 71. 72 orthe like for opening normally closed contacts 73. 74 f microsw tches 767' c e c revolution of the cams. The clutches 66 67 are mechanicallylinked to timer relays 78. 79 so as to be engaged upon actuation of thelatter. More specifically. relays 78, 79 respectively comprise operatingcoils 81, 82'. and sets of contactors 83, 84 and 86. 87 operable betweennormally closed contacts 88. 89 and 91, 92 and normally open contacts93, 94 and 96, 97, the contactors being linked with the respectiveclutches 66. 67. Thus, upon energization of the coil of either of therelays 78. 79 in a manner subsequently described, the corresponding oneof the clutches 66, 67 is responsively engaged and the associated motorand cam are connected. Hence upon completion of one revolution of thecam. the normally closed contacts of the corresponding one ofmicroswitches 76, 77 are instantaneously opened. The time intervalsbetween engagement of the clutches and opening of the microswitchcontacts in the respective timers is utilized herein as the timedintervals of the alert and take-cover warning signals. Moreparticularly, the relays and microswitches of the timers areappropriately interconnected to provide lock-up circuits whereby uponthe instantaneous energization of the respective timer relay coils,locked in energization of the coils is maintained for the time intervalsdetermined by the rotating cams, the relays being arranged to berestored upon the instantaneous opening of the microswitches. To providesuch lock-up circuits, the normally closed contacts 73 of microswitch 76are connected in series between normally open contact 93 and one side ofcoil 81 of alert timer relay 78 whereas contacts 74 of microswitch 77are similarly con-. nected between normally open contact 94 and one sideof coil 82 of take-cover timer relay 79. The other sides of the relaycoils are in turn connected to ground. The operating current forsustaining energization of the relay coils is derived from the lowvoltage direct current output of the power supply 27, the commonjuncture of rectifiers 42, 43 being connected to contactors 83, 86 ofrelays 78, 79, respectively.

By virtue of the foregoing connections, upon instantaneous energizationof the coils of relays 78, 79, the contactors 83, 86 engage normallyopen contacts 93, 94 to thereby apply operating current to the relaycoils through the normally closed micro switch contacts 73, 74,respectively. Actuation of the relays also eifects engagement of therespective clutches 66, 67 whereby the earns 68, 69 are driven by themotors 58, 59. Upon completion of a revolution of cam rotation, thepawls 71, 72 instantaneously open the respective micro switch contacts73, 74 to thereby interrupt the flow of operating current to the coils81, 82 and restore the timer relays to their normal unenergizedconditions. It will thus be appreciated that the lock-up time intervalsof the timers may be manually varied in a manner well known in the artas by changing the ratio of adjustable gearing in timer clocks (notshown) employed with the motors to vary their output shaft speeds.

As regards the connections of the timers 56, 57 in energizing relationto the power supply control relay 44 such that it is operated in concertwith the timers and therefore during the respective time intervalsthereof, the normally open contacts 94, 97 of timer relays 78, 79respectively, are connected to one side of the operating coil 46 ofrelay 44, the other side thereof being connected to ground. In addition,contactors 84, 87 of the respective timer relays are connected to theother contactors 83, 86 thereof so as to be likewise energized with theoperating voltage derived from rectifiers 42, 43. Thus, upon actuationof either timer, the power supply control relay 44 is actuated for theduration of the corresponding timed interval thereof to effect timedoperation of the tone oscillator circuit 18.

In order that the foregoing operation of the timers 56, 57 and toneoscillator circuit 18 be selectively initiated in response to actuationof the alert and takecover control push buttons 12, 13 or to remoteswitching means, the timer relay coils 81, 82 are respectively connectedthrough the alert and take-cover control push buttons to the low voltagedirect current output provided by rectifiers 42, 43 of power supply 27.In addition, the push button switches 12, 13 are respectively connectedacross sets of pins of the control outlet 14 to facilitate alternativeaccomplishment of their switching functions by other switching means asmay be connected to the control outlet. Thus, the requisite initialmomentary energization of the timer relay coils is selectivelyaccomplished upon closure of the alert or take-cover control pushbuttons12, 13 or alternative switching means coupled to the control outlet 14.

To facilitate control over the tone oscillator circuit 18 in theselection of the type of signal generated therefrom (steady or wailingtone), control over the input of a sound system such as includesamplifier 16 to insure priority of the generated air-raid-warningsignals over a program source such as microphone 17, and priority of thetake-cover signal over the alert signal, alert and take-cover mastercontrol relays 98, 99 are I responsively connected to the alert andtake-cover push 1S 396D) include an operating coil 101 and contactors102, 103 respectively operative between normally closed contacts 104',106' and normally open contacts 107, 108. One side of coil 101 isconnected to ground. Contactor 102 is connected to ground while normallyopen contact107, is connected to the high side of bias. capacitor 24 ofthe slow tuning tone oscillator section 21 of tone oscillator circuit18. Thus, upon actuation of alert master control relay, the capacitor 24is shorted to ground through contactor 102 and contact 107 totherebymute the wailing tone function of oscillator section 21 such thatthe steady tone alert signal is generated by the oscillator circuit.Normally closed contact 106 is connected to a program source terminal109 of audio. outlet 11, the microphone 17 being connected between thisterminal and a grounded shield terminal 111.

Take-cover master control relay 99 includes, an opcrating coil 112 andcontactors 113, 114, respectively operative between normally closedcontacts. 116, 117' and normally open contacts 118, 119. The coil 112 isconnected at one side to ground and at the other side through take-covercontrol push button 13 to the low voltage direct current output of powersupply 27. This latter side of the coil is also connected to thecontacts of the take-cover timer micro switch 77'. The normally closedcontact 116. is connected to contactor 103' of alert master controlrelay 98 while normally open contact 118 is connected to normally opencontact 108 of the latter and to the output of tone oscillator circuit18 at volume control 26. The contactor 113 is connected to an audiooutput terminal 121 of audio. outlet 11, the input of audio amplifier 16being connected between such terminal and shield terminal 111. Normallyclosed contact 117 is connected to the ungrounded side of the operatingcoil 101 of alert master control relay 98 while contactor 114 isconnected through alert control push button 12 to the low voltage directcurrent output of power supply 27. Contactor 114 is also connected tothe contacts of the alert timer micro switch 76. It will thus beappreciated that with the foregoing connections of the control relay 98,99, the microphone or other program source is connected to. the audioamplifier 16 through a current path including normally closed contact106, contactor 103, normally closed contact 116, and contactor 113. Uponenergization of either master control relay, the current path is openedby virtue of contactor 103 or contactor 113 moving into engagement Withthe associated one of normally open contacts 108, 118. Since both ofthese normally open contacts are connected to the output of the toneoscillator 18,. the tone signals therefrom are at this time applied tothe. audio amplifier with priority over the microphone. Furthermore, itis to be noted that inasmuch as the normally open contact 108 of alertrelay 98 is connected to the audio amplifier through the normally closedcontact 116 and contactor 113 of takecover relay 9.9, and energizationof coil 101 of the alert relay is through contactor 114 and normallyclosed contact 117- of the take-cover relay, priority of a take-coversignal over an alert signal is obtained. More specifically, were thealert master control relay 98 actuated and an alert signal beingdelivered to the audio outlet, upon actuation of the take-cover mastercontrol relay 99 the contactor 113 moves into engagement with contact116 to thereby interrupt the alert signal and deliver the take-coversignal to the audio amplifier, and contactor 114 moves out of engagementwith contact 117 to hence deenergize the alert relay coil 101.

In the overall operation of the air-raid-warning signal generator 10,the power supply 27 energizes the filaments of the duo-triod'es 22, 23of the tone oscillator circuit 18 and the motors 58, 59 of the alert andtake-cover timers 56, 57 are running when the generator is in a stand-bycondition. Where the generator is employed with an existing sound systemsuch as includes audio amplifier 16, the amplifier 16 may be used in itsusual manner with microphone 17 or other program sources when the signalgenerator is in stand-by condition. Assuming now that the alert controlpush button 12 is actuated or alert switching is accomplished from acentral command location through a command circuit wired to controloutlet 14', the alert master control relay 98 and alert timer relay 78are responsively actuated. Relay 98 disconnects the microphone 17 orother program source from audio amplifier 16 and connects the output oftone oscillator circuit 18 thereto. This relay also mutes. the output ofthe slow tuning oscillator section 21 such that the tone oscillatorcircuit is prepared to generate a steady tone signal. The timer relay 78simultaneously is locked up for its preset timing interval of, forexample, four minutes as determined by the rotational period of cam 68.The power supply control relay 44 is in turn actuated for the timedfour-minute interval to provide plate bias to the tubes of the toneoscillator circuit 18 and place same in operation. The oscillatorcircuit 18 hence generates a steady tone alert signal during the timedfour-minute interval and such signal is applied to the audio amplifier16; Ex.- ternal' circuits connected to the control outlet 14 are alsoswitched during the interval by the relay 44. When the interval is timedout by the alert timer 56, all relays are restored by the, momentaryopening of the normally closed contacts 73 of micro switch '7 6.

When the take-cover control push button 13 is momentar-ily closed ortake-cover switching is otherwise accomplished, the take-cover mastercontrol relay 99 and take-cover timer relay 79 are instantaneouslyactuated and thereafter are. energized through the normally closedcontacts 74 of the take-cover timer micro switch 77 during the locked uptime interval of, for example, three minutes established by the timer.The take-cover master control relay 99 disconnects the microphone 17from audio amplilier 16 and connects the output of tone oscillatorcircuit 18 thereto. It is particularly important to note that relay 99also locks out the operating coil 101 of alert master control relay 98such that in the event the alert signal was being generated at the timeit was desired to sound the take-cover signal, the take-cover signalwould be automatically given priority. The power supply control relay 44is actuated by the take-cover timer relay 79 for the timed locked upinterval of the timer 5-7 to provide plate, bias voltage to the tubes ofthe tone oscillator circuit 18 and place same in operation. Since thecapacitor 24 of the slow tuning oscillator section 21 is not grounded.at this time, the wailing take-cover tone signal is generated by theoscillator circuit and applied to the audio amplifier 16 during thetimed interval of the take-cover timer 57. External circuits connectedto the control outlet 14 are also switched during the interval by thepower supply control relay 44. When the interval is timed out by thetimer 57, all relays are restored by the momentary opening of thenormally closed con tacts 74 of the take-cover timer micro switch 77,.

What is claimed is:

1. An air-rarid-warning signal generator comprising a tone oscillatorcircuit for selectively generating steady and wailing tone signals,power supply means for generating operating bias for said toneoscillator circuit, first and second timed interval switching meanscoupling said,

power supply means to said tone oscillator circuit and; operable toapply said operating bias to the tone oscillator circuit during theirrespective timed intervals in response to steady and wailing toneactuating signals, and selector means coupled to said oscillator circuitand said first and.

second timed interval switching means for selecting a steady tone signalin the oscillator circuit simultaneously with the application of asteady tone actuating signal to said timed interval switching means anda wailing tone signal in the oscillator circuit simultaneously with theapplication of a wailing tone actuating signal to the timed intervalswitching means.

2. An air-raid-warm'ng signal generator comprising a 7 generation ofsteady tone or wailing tone signals, power supply means coupled to saidoscillator circuit for applying operating bias thereto uponenergization, steady and wailing tone timers coupled to said powersupply means coupled to said oscillator circuit for applying operatingbias thereto upon energization, steady and wailing tone timers coupledto said power supply means for upon actuation energizing said powersupply means for predetermined steady and wailing tone timed intervalsand selective steady and wailing tone actuating means coupled to theselecting means of said tone oscillator circuit and said timers foractuating the selecting means to steady tone generation simultaneouslywith actuation of said steady tone timer and actuating the selectingmeans to wailing tone generation simultaneously with actuation of saidwail ing tone timer.

3. An air-raid-warning signal generator comprising a tone oscillatorcircuit including a steady tone oscillator section and slow tuningoscillator section for generating a steady tone signal with wailing tonesignal superimposed thereon, power supply means coupled to saidoscillator circuit for applying operating bias thereto upon actuation,an interval timer operatively coupled to said power supply means uponactuation responsively to actuate the power supply means for apredetermined time interval, a second interval timer operatively coupledto said power supply means upon actuation responsively to actuate thepower supply means for a predetermined second time interval, steady tonecontrol relay means coupled to the slow tuning oscillator section ofsaid tone oscillator circuit and to said first timer, said relay meansoperable upon actuation to mute said slow tuning oscillator section andactuate said first timer, wailing tone control relay means coupled tosaid second timer and operable upon actuation to responsively actuatesame, steady tone selector means coupled to said steady tone controlrelay means for selectively actuating same, and wailing tone selectormeans coupled to said wailing tone control relay means for selectivelyactuating same.

4. An air-raid-warning signal generator according to claim 3, furtherdefined by said steady tone and wailing tone control relay meansrespectively including first and second current paths with the firstpaths being normally closed and the second paths being normally open,said second paths being closed upon actuation of the respective relaymeans simultaneously with opening of the first paths, and an audiooutlet having program source terminals and sound system input terminals,said program source terminals serially coupled to said sound systemterminals through the first paths of said steady and wailing tone relaymeans, said sound system terminals serially coupled to the output ofsaid tone oscillator circuit through the second paths of said steady andwailing tone relay means.

5. An air-raid-warning signal generator comprising an electronic toneoscillator circuit including a steady tone oscillator section and slowtuning oscillator section for generating a steady tone signal withwailing tone signal superimposed thereon; power supply means having afilament output coupled to the tubes of said oscillator circuit and aplate bias output; power supply control relay means coupled between saidplate bias output and said oscillator circuit, said power supply controlrelay means operable upon energization to apply plate bias to the tubesof said oscillator circuit; an interval timer coupled to said powersupply control relay means and operable upon energization to energizesaid power supply control relay means for a predetermined time interval;a second interval timer coupled to said power supply control relay meansand operable upon energization to energize said power supply controlrelay means for a predetermined second time interval; steady toneselector switch means coupled in energizing relation to said first timerto ener gize the timer upon momentary actuation of the switch means;wailing tone selector switch means coupled inenergizing relation to saidsecond timer to energize said 8 second timer upon momentary actuation ofthe wailing tone switch means; a wailing tone control relay responsivelycoupled to said wailing tone selector switch means and to said secondtimer, said wailing tone control relay relay having first and secondcontactors operable between first and second normally closed andnormally open contacts, said first contactor responsively coupled tosaid steady tone selector switch means and to said first timer, saidsecond normally open contact coupled to the output of said toneoscillator circuit; a steady tone control relay responsively coupled tothe first normally closed contact of said wailing tone control relay,said steady tone control relay having first and second contactorsoperable between first and second normally closed and normally opencontacts, said first contactor connected to ground and said firstnormally open contact coupled to said tone oscillator circuit to mutethe output of the slow tuning oscillator section thereof in response togrounding, said second contactor coupled to the second normally closedcontact of said wailing tone control relay, said second normally opencontact coupled to the output of said tone oscillator circuit; and anaudio outlet having program source and sound system input terminals,respectively, coupled to the second contactor of said wailing tonecontrol relay and to the second normally closed contact of said steadytone relay.

6. An air-raid-warning signal generator according to claim 5, furtherdefined by said first and second timers each comprising a synchronousmotor, a cam, a clutch mechanically coupling said cam to said motor, amicro switch having normally closed contacts engageable by said cam forinstantaneous opening each cam revolution, and a relay mechanicallylinked with said clutch to engage same upon relay actuation, said relayhaving an operating coil and first and second contactors operablebetween first and second normally closed contacts and normally opencontacts, said coil serially connected with said micro-switch contactsand first normally open contacts; a power source connected in energizingrelation to the coils of the first and second timer relays throughrespectively said steady tone selector switch means and wailing toneselector switch means; means connecting said power source to said firstand second contactors of said first and second timer relays; meanscoupling the micro-switch contacts of said second timer in energizingrelation to said wailing tone control relay; means connecting themicro-switch contacts of said first timer to the first contactor of saidwailing tone control relay; and means coupling the micro-switch contactsof said first and second timers in energizing relation to said powersupply control relay means.

7. An air-raid-warning signal generator comprising an electronic toneoscillator circuit including first and second multivibrator connectedtubes with the second tube having a bias capacitor coupled between itsgrids and ground to slowly vary the tone of the output therefrom; apower supply including a transformer with secondary tapped to provide alow voltage filament output and high voltage rectifier plate andfilament outputs, a full wave rectifier having its plates and filamentconnected to said high voltage rectifier plate and filament outputs, andopposed rectifiers connected between said low voltage filament output;means connecting said low voltage filament output to the filaments ofthe tubes of said tone oscillator circuit and the output of saidfull-wave rectifier to the plates thereof; a power supply control relayhaving an operating coil and first and second contactors operativebetween first and second normally closed and normally open contacts, oneside of said coil and said first contactor connected to ground, saidfirst normally open contact connected to a center tap between the highvoltage rectifier plate output taps of the transformer secondary of saidpower supply; a control outlet having eight terminals with the firstconnected to ground, the second to the eighth, the fifth, sixth andseventh to the second normally open contact, second contactor, andsecond nor- 9 mally closed contact of said power supply control relay; asteady tone control push button connected between the third and eighthterminals of said control outlet; a Wailing tone control push buttonconnected between the fourth and eighth terminals of said controloutlet; means connecting the common juncture of the opposed rectifiersof said power supply to said eighth terminal of said control outlet; 21first timer having an actuating input and timed interval output, saidactuating input coupled to the third terminal of said control outlet,said timed interval output connected to the operating coil of said powersupply control relay; a second timer having an actuating input and timedinterval output, said actuating input coupled to the fourth terminal ofsaid control output, said timed interval output connected to theoperating coil of said power supply control relay; an audio outlethaving a grounded shield terminal connected tothe first terminal of saidcontrol outlet and a program source terminal and sound system inputterminal; a Wailing tone control relay having an operating coil andfirst and second contactors operative between first and second normallyclosed and normally open contacts, said coil connected between saidfirst and fourth terminals of said control outlet and to the timedinterval output of said second timer, said first contactor connected tothe third terminal of said control outlet and to the timed intervaloutput of said first timer, said second contactor connected to the soundsystem input terminal of said audio outlet, said second normally opencontact connected to the output of said tone oscillator circuit; and asteady tone control relay having an operating coil and first and secondcontactors operative between first and second normally closed andnormally open contacts, said operating coil connected between the firstterminal of said control outlet and the first normally closed contact ofsaid wailing tone control relay, said first contactor connected toground, said first normally open contact connected to the high side ofthe bias capacitor of said tone oscillator circuit, said secondcontactor connected to the second normally closed contact of saidwailing tone control relay, said second normally closed contactconnected to the program source terminal of said audio outlet, saidsecond normally open contact connected to the output of said toneoscillator circuit.

No references cited.

